1. Field of the Invention
This invention relates to finishing interior walls. In particular, this invention relates to finishing the edges at intersections where two walls meet.
2. Statement of the Problem
Drywall panels are widely used in the construction industry for foraging the interior walls and ceilings of rooms. Drywall panels are made of a gypsum or reinforced gypsum core covered with paper. Drywall panels have the advantages of being easy to cut to desired sizes and to attach to assorted types of framing. However, it is very difficult to cut drywall panels so that the edges are perfectly straight and smooth and can meet to form a perfectly straight corner, which is aesthetically to be desired. In addition, when the drywall panels are cut to the desired sizes, the edges of the panels are left exposed. This exposed gypsum core is soft and tends to crumble unless the severed edges are somehow protected. This is especially important at outside wall corners.
When walls and ceilings are built of framing materials such as wood, the inside and outside corners thereby formed are seldom perfectly straight. Small variations in the sizes of the wood framing members, warping of the wood, and inconsistent building practices lead to imperfectly straight corners where walls and ceilings meet, and where walls end at doorways and passageways. When drywall panels are then attached to the crooked framing materials, their intersections will also be crooked.
An assortment of devices have been used to provide a smooth and durable finish for the intersections where two pieces of drywall abut to form an inside or outside corner. Among the conventional devices used are drywall tape and metal corner beads. Conventional drywall tape is provided in narrow, elongated ribbons or strips of porous paper wound into rolls. The paper is sometimes perforated to increase moisture penetration and to prevent air bubbles from being entrapped behind the tape. The drywall tape is first applied to joints and edges of abutting drywall panels and is then covered with wet plaster, sometimes called "mud." The plaster is feathered and smoothed along the edges of the tape to conceal the demarcations between the tape edges and the drywall panels to which the tape is applied. When the wet plaster has dried, the tape and drywall can be painted or otherwise covered with a suitable wall covering.
A great deal of skill is needed to apply the plaster to both sides of an inside corner such that a perfectly straight intersection is achieved. Also, to correct the crookedness resulting from the warped framing members and inconsistent building practices described above, often several coats of plaster must be applied, with an entire day of drying time needed between each coat. Even then, a perfectly straight corner seldom results. It is also likely that, unless in the most highly skilled hands, the plaster trowel will mar the first side of the plaster while the second side is being applied. Once the plaster has been applied and dried, it must be sanded to an appropriate finish to provide a surface suitable for the application of paint or wallpaper.
Coffered and vaulted ceilings have recently become very popular among home builders and buyers. Often the peak of such ceilings will form an acute angle. It is difficult to fit a conventional plaster trowel into such angles.
Because drywall tape is formed of paper, it is quite flexible and will conform to various surface configurations of the edges of intersecting panels of drywall. When conventional drywall tape is used at the outside corners of walls, the flexibility of the tape often results in a corner demarcation that is irregular, since the tape conforms to irregularities in the exposed, severed edges of the drywall panels. The tape is also fragile and does not stand up well to the constant physical abuse suffered by outside corners. As a consequence, conventional drywall tape cannot be used at exposed outside corners.
To finish outside corners in building construction, therefore, metal corner beads are often used. Conventional metal beads are configured in an L-shaped or angle-shaped cross section and are typically fabricated from elongated perforated strips of metal, such as galvanized steel, permanently deformed with a lengthwise 90-degree bend to form elongated angles. The metal beading is typically positioned at the intersections of adjacent drywall panels that meet at right angles to form an outside corner within a room. The sections of metal beading are nailed in place through the drywall panels to wooden supporting structural members located behind the drywall panels. Wet plaster is then smoothed into place to cover the metal flanges or leg members of the metal beading, and the edges of the plaster are smoothed and feathered to attempt to conceal the metal edges.
While the rigidity of the metal beading does allow an outside corner of an inside building wall to be finished with a sharp, straight edge, which is aesthetically pleasing, the use of metal beading involves some significant problems. Over time, the metal corner bead will rust, thereby producing rust stains that are clearly visible on the surfaces of the walls at the corner. It is not always possible to completely cover the edges of the metal flanges or the nail heads used to attach the metal corner bead to the drywall panel, detracting from the desired smooth appearance of the wall. Cracks often develop in the overlying plaster at the outer edges of the flanges. To prevent this from happening, often two or three coats of plaster are applied, with prior coats allowed to dry and harden, which may take as long as 24 hours, before a subsequent coat is applied. When the corners are crooked or jagged due to problems with the underlying framing, metal beads do not cover enough surface area or have enough flexibility to correct the inequalities that exist. Another problem is inherent in the fact that the malleable metal from which the metal beads am made has a very poor memory and is subject to being dented or wrinkled, after which it is difficult to straighten it to produce a smooth finish. Because of the rough handling to which most of the material at a work site is subjected, it is not uncommon for the strips to be wrinkled, dented, and perhaps twisted, thus rendering them either unusable, or usable only to produce an inferior end result. In addition, the metal strips are used in large quantities in construction and can add up to considerable cost.
A number of corner finishing devices have been developed to address the above-described problems. Among these devices are the following:
______________________________________ Inventor U.S. Pat. No. Date issued ______________________________________ Swanson 3,444,657 May 20, 1969 Baker 3,989,397 Nov. 2, 1976 Ellingson 4,012,878 Mar. 22, 1977 Lamb 4,313,991 Feb. 2, 1982 Schaafsma 4,315,390 Feb. 16, 1982 Weinar 4,553,363 Nov. 19, 1985 Schneller 4,624,087 Nov. 25, 1986 Bernard 4,719,732 Jan. 19, 1988 Tucker 4,863,774 Sept. 5, 1989 Conboy 5,037,686 Aug. 6, 1991 Tucker 5,045,374 Sept. 3, 1991 Weldy 5,086,598 Feb. 11, 1992 Ritchie et al. 5,131,198 July 21, 1992 ______________________________________
Swanson and Lamb describe plastic joint strips that can be reversibly bent to be adhesively secured to both inside and outside corners.
Baker shows an outside corner connector for waterbed pedestals in which the panels forming the pedestal are inserted into the connector.
Ellingson provides a double-layer wall member guard structure for outside corners made of a resilient material.
Schaafsma describes two types of wallboard corners, one for inside corners that is held in place by putty and another for outside corners that is held in place by the drywall panels themselves. The former is disadvantaged by the fact that it is held on only by putty; if the putty does not adhere well to the drywall, the corner will become loose. The outside corner must be placed under the drywall panels, involving considerable bending or, if placed on the corner before the panels, a certain amount of extra effort to hold the corner in place while the panels are being nailed over it. Both corners use tape to provide a smooth top finish that can be blended in with the drywall finish by applying plaster and sanding.
Weinar provides a plastic or metal T-shaped corner construction in which the post of the T sits between two abutting pieces of drywall and the cross bar lies atop the drywall panels. Part of the paper covering from one panel is wrapped around the cross bar to provide a finished appearance, leaving a ridge down one side of the corner. This corner construction can only be used on outside corners.
Schneller describes yet another type of metal outside corner bead in which an additional flange extends over the edge of the drywall board forming the outside corner. Ridges are left on both sides of the corner, and this corner bead can only be used on outside corners.
Bernard presents a plastic L-shaped outside corner cover that uses heat-shrinkable plastic tape along the anus both as a method of attachment and as a method of providing a smooth junction between the cover and the drywall. This cover can be used for outside corners having a variety of angles.
Tucker provides a paper drywall ribbon having a centrally located plastic bead extending longitudinally along the ribbon. Plaster is used to attach the ribbon to the drywall. This plastic bead is designed to be used with outside corners only.
Conboy describes a plastic drywall tape that can be used on both inside and outside corners. Again, this plastic tape is held on the corner with plaster, and plaster is used to provide a finished appearance.
Tucker describes a stiff plastic strip with a curved center section and two flanges that is attached to outside or inside corners with adhesive. The flanges are then covered with paper tape strips and plaster.
Weldy provides a wall edging system for both inside and outside corners that comprises a plastic strip having an arcuate center portion to which are attached two flanges at right angles. The strip is attached to the drywall with nails. Plaster is then smoothed over the strip to finish the edges. The side of the strip facing out toward the room can be finished with primer.
Ritchie et al. describe a corner bead for outside corners that has a metal core and that is completely covered by paper. This bead has a rounded nose and side flanges. The paper covering is further coated with a reinforcing emulsion. The corner bead is nailed to the drywall, and plaster is used to hide the edges.
A need exists for a drywall corner finishing device that can be used on both outside and inside corners having various angles and that provides a primed surface for either orientation. A further need exists for a drywall corner finishing device that can be used to cover juxtaposed outside corners, such as are found at the edges of interior doorways or other openings of various dimensions, for example, passthroughs from one room to another. Because of the crooked corners that result from warped building materials and inconsistent building practices, a need exists for a corner finishing device that will provide a perfectly straight corner without the use of multiple coats of plaster. A finishing device is also needed that will simplify installation of drywall in acutely angled inside corners and minimize the need to use plaster. None of the above-described drywall corners fulfills these needs.
3. Solution to the Problem
The drywall corner finishing device described herein can be used for both inside and outside corners having various angles. Builders will not have to order two or more versions to cover different types of corners. The drywall corner finishing device described herein can also be used to cover two adjacent outside corners without requiring the use of a narrow strip of drywall panel between the corners and two finishing devices, one for each outside corner. A layer of primer or laminate covers the side of the drywall corner finishing device of the present invention that faces into the room. Because of this primer or laminate layer, plaster need only be used on the outside edges of the corner finishing device where it abuts the drywall. The drywall corner finishing device described herein has a width generally equal to that of the drywall panels, so that little plaster is needed to fill in the area where the drywall panels meet the finishing device. The drywall corner finishing device of the present invention is capable of hiding crooked, uneven corners no matter how irregular the deviations may be. The present drywall corner finishing device is nailed directly to the framing members of the wall, thereby providing stability.